Transfer printing and laminating blanket

ABSTRACT

A dual purpose transfer printing and laminating blanket (18) has an endless woven base fabric (28) having at least one layer of fluoropolymer coating material (32, 33) applied thereto. A bonding layer is applied to each side of the base fabric, to bond the at least one layer to the base fabric.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transfer printing and laminatingblanket.

2. Description of Related Art

Transfer printing is usually carried out using a calender-type machineequipped with an endless NOMEX (R.T.M.) needlefelt blanket. The blanketcomprises a woven basecloth onto which one or more layers of staplefibres are applied by needling. The blanket generally comprises astandard polyester, NOMEX (R.T.M.) OR KEVLAR (R.T.M.) basecloth ontowhich high temperature resistant staple NOMEX (R.T.M.) fibres areneedled.

It is proposed that a calender-type transfer printing machine be usedboth for transfer printing and laminating. A conventional transferprinting blanket would be unsuitable as a dual purpose transfer printingblanket and laminating belt. This is because these known needlefeltblankets would be readily contaminated by the hot melt adhesives usedduring the laminating process. The contaminants would pose a problem inthe transfer printing process. In view of this silicone coated blanketshave been proposed, but these have proven to be unsuccessful because ofthe temperature, chemical and physical limitations of silicone rubber atthe operating temperature of the calender machines which may be as highas 260° C.

SUMMARY OF THE INVENTION

The present invention seeks to provide a blanket, to be used for bothtransfer printing and laminating, which offers a satisfactory solutionto the problem of hot melt adhesive contamination.

According to the present invention there is provided a dual purposetransfer printing and laminating blanket, said blanket comprising anendless woven base fabric and at least one layer of a fluoropolymercoating material applied thereto.

The blankets of the invention achieve as good a print as is achievedwith the traditional blankets as described herein, but substantiallyavoid the potential problems of contamination of such traditionalblankets owing to the smooth, non-stick impermeable fabric surface. Theblankets of the invention further exhibit superior heat resistance,chemical inertness, hardness and suppleness.

The thickness of the fabrics of the invention is preferably at least 1.5mm and is more preferably in the range from 1.5 mm to 7 mm.

The coating may include silicate bodies therein thereby to mask thefabric interstices and substantially avoid manifestation of the basefabric at the belt surface. Ideally, the silicate bodies comprise glassbeads having a diameter in the range 2 to 200 microns. Preferably thesilicate bodies have a diameter monosized at approximately 90 microns.Multiple coating layers may be provided. Ideally the silicate bodiesexist in each coating layer in like amount by weight to the coatingmaterial. More preferably the multiple thin layers include at least onebonding layer applied to the woven base fabric.

The coating is preferably applied to any one side of the fabric,preferably the face side, but may be applied to both sides. Thepreferred method of coating includes the use of a doctor blade.Alternatively, the fabric coating may be provided by means of dip and/orlick coating. The upper layer of fluoropolymer coating may contain metalpowder, for example of stainless steel, bronze or nickel, to reflectheat back into the article being the subject of the transfer printing orlaminating process.

The fabric may typically have a semi-triplex of plain weave structure,optionally with one or more layers of fibres needled onto one side,usually the backside of the fabric. Examples of suitable fabricmaterials include any of the following either alone or in combination:glass, ceramic, metal, PEEK, meta- and para-aramid fibres, filaments andspun yarns. Width stability to avoid blanket creasing can be improved,particularly for wide blankets, by incorporating metal wires, forexample stainless steel or bronze, into the fabric. These wires can runin either or both of the machine direction or cross-machine direction ofthe fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be more readily understood aspecific embodiment thereof will now be described by way of example onlywith reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic view of a calender machine equipped with ablanket in accordance with the present invention;

FIG. 2 illustrates the method steps for making the blanket shown in FIG.1; and

FIG. 3 is a longitudinal section taken through the blanket in accordancewith the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 a calender machine 10 comprises a rotating drum 11heated to 200° C. The heat from the drum 11 acts upon a sheet ofsublimistic paper 12 which is fed around the drum 11 from a first set ofrollers 13 to a second set of rollers 14. The sublimistic paper is apattern-embossed paper supporting sublimistic dyestuffs. A sheet ofmaterial 15 which is to be printed, such as a knitted polyester fabric,is passed over the sublimistic paper from a first set of rollers 16 to asecond set of rollers 17.

An endless transfer printing blanket 18 extends over a series of rollers19. The transfer printing blanket urges the material to be printedagainst the sublimistic paper.

When in operation the heated drum 11 heats the dyestuffs which sublimeand re-form on the material to be printed, thus transferring the patternof the sublimistic paper to the material to be printed. The transferblanket is used to ensure that a uniform print is applied to thematerial.

The calender member 10, may be used for laminating by substituting thesublimistic paper for a hot melt adhesive film in order to apply the hotmelt film to a fabric.

Referring now to FIGS. 2 and 3 in coating a woven base fabric to providea transfer printing blanket 18 an endless woven fabric 19 is supported,under tension, on a plurality of horizontal rollers 20,21,22 arranged inspaced apart disposition above a supply of coating material contained ina tank 23 and is successively engaged with and withdrawn from coatingmaterial 24 present in the tank 23 to take up material therefrom.

Conveniently the tank 23 is raised or lowered so as to bring the coatingmaterial 24 into contact with the blanket 18 for the time being existingon the rollers 20,21,22, the extent of movement being such as to causethe lower part 26 of the blanket 18 to become immersed in the coatingmaterial 14 or simply to engage the surface 27 thereof according to thenature of the coating step required.

In the arrangement illustrated three rollers are provided, two suchrollers 20,21 being arranged at a common level and serving to supportthe fabric 19/blanket 18 and the third roller 22 being at a lower leveland operating as a guide roller to position the lower part 26 of thefabric/belt. At least one of the upper rollers 20,21 is driven so as torotate the fabric/belt about the roller arrangement.

The process steps are shown in FIG. 2 and comprise, in succession, dipcoating steps, FIGS. 2b to 2e, a lick-coating step, FIGS. 2f and 2g,two-dip-coating steps, FIGS. 2h to 2k, and a further lick-coating step,FIGS. 21 and 2m, each step including drying/sintering of the appliedlayer, FIGS. 2c, 2e, 2g, 2i, 2k and 2m.

The base fabric 28, see FIG. 3, is of plain weave construction and iswoven from 1100 d.tex Kevlar (R.T.M.) or Technora (R.T.M.)multi-filament yarns 29,30 from the warp and weft densities in the loombeing 11.22 and 9.45 yarns/cm. The fabric weight is 225 grams/meter² andthe fabric thickness is 0.36 mm.

On tensioning of the base fabric the length thereof increases byapproximately 1.9% whilst the width reduces by approximately 4.4%, thefabric thickness increasing to 0.43 mm.

The initial dip coating steps serve to apply a bonding coat 31 to thebase fabric 28 and the mix is merely a polytetrafluoroethylene bondingmaterial. For the initial lick coating step, which step forms coatinglayer 33 at the support side of the base fabric, and the remaining dipcoating steps, which apply coating material to both sides of the fabric,that is to say for the weave filling steps which form coating layers32,34 at the respective sides of the fabric, the mix also includessilicate bodies, typically solid glass beads having a diameter ofbetween 53 and 105 microns but preferably monosized at approximately 90microns. Indeed, it is believed that the use of monosized beads offersimproved weave filling as compared with the use of beads of a sizerandomly distributed with a range of diameters. Typically, the silicatebodies are present in the relevant coating layers in like amount byweight to the dried/sintered P.T.F.E. coating material. The finalcoating step applies a top coat 35 of P.T.F.E. having metallicparticles/flake included therein. An additional weave final coating stepwill ordinarily be applied, notwithstanding that such additional step isnot shown in FIG. 2.

Thus, the bonding coat 31 consists of two layers at each side of thebelt to give a total coating weight of 250 grams/meter² whilst the weavefilling coats 32,33,34 which respectively comprise three coating layersand two coating layers, have a total weight of 400 grams/meter². Thefinal or top coats 35, each of which comprises two layers, have a totalweight of 100 grams/meter². The finished thickness of the coated belt is0.69 mm.

The blanket is illustrated diagrammatically in FIG. 3, it being seenthat the bonding layers, which layers promote adhesion of the subsequentcoating layers to the base fabric, permeate the surface of themultifilament yarns and bridge the interstices in the fabric and thatthe glass beads serve to fill the recesses in and defined by the bondinglayers to give a substantially flat outer surface to the beltparticularly at the support side thereof, the top coating being ofsensibly constant thickness and thus having a surface form of similarcharacter to that formed by the weave filling layers. It will beappreciated, of course, that, after coating, the belt will becalendered.

The blanket of the invention is not restricted to the detail of theembodiment hereinbefore described, since alternatives will readilypresent themselves to one skilled in the art. Thus, for example, whilstthe bonding coats do improve adhesion of the weaving filling layers tothe base weave, the bonding coats may, in some circumstances, beomitted.

The number of weave-filling layers may be varied according to specificrequirements and more than one such layer may be applied by lickcoating. The solids content of the PTFE dispersion may be other than 50%indeed an increased solids content, say to 70%, is desirable as thisreduces the tendency of the coating to contour the fabric weavestructure. The increased solids content also facilitates weave fillingand drying/sintering of the PTFE, and has advantageous effects on thethermal characteristics of the belt in use.

Other weave constructions and other yarns, for example glass yarns, may,of course, be used, and the PTFE coating material may include suchadditives as are appropriate to introduce requisite characteristics intothe belt according to its intended end use. For example, it may be foundconvenient to use metallized beads, whether in the weave filling layersand/or in the top coat, and thus dispense with the need to includemetallic particles/flake in the top coat.

I claim:
 1. A dual purpose transfer printing and laminating blanketcomprising an endless woven base fabric, at least one coating layerapplied to each side of said base fabric and at least one top coatprovided over said coating layers on each side of the base fabric, atleast one of said top coat comprising a fluoropolymer material andproviding a smooth and substantially flat outer support surface.
 2. Adual purpose transfer printing and laminating blanket according to claim1, wherein at least one of said coating layers include silicate bodiestherein, to thereby mask the interstices of the woven base fabric andsubstantially avoid manifestation of the base fabric at the beltsurface.
 3. A dual purpose transfer printing and laminating blanketaccording to claim 2, wherein said silicate bodies comprise glass beadshaving a diameter in the range from 2 to 200 microns.
 4. A dual purposetransfer printing and laminating blanket according to claim 3, whereinthe silicate bodies have a substantially uniform diameter ofapproximately 90 microns.
 5. A dual purpose transfer printing andlaminating blanket according to claim 1, wherein the blanket has athickness of from 1.5 to 7.0 mm.
 6. A dual purpose transfer printing andlaminating blanket according to claim 1, wherein each said coating layerincludes silicate bodies which comprises or includes a fluoropolymermaterial.
 7. A dual purpose transfer printing and laminating blanketaccording to claim 6, wherein the silicate bodies are provided in eachcoating layer in approximately equal proportions.
 8. A dual purposetransfer printing and laminating blanket according to claim 1, whereinthe fluoropolymer coating includes metal powder.